Patent GB-430453-A (GB)
Title: Improvements relating to telegraph signalling apparatus
IPC: H04L1/08
Filed: 1934-04-10
Abstract: 430,453. Code telegraphy wireless signalling. MASSON, A. H., 28, Victoria Park Road West, Cardiff. April 10, 1934, No. 10814. [Classes 40 (iii) and 40 (v)] In a system in which the effects of disturbance or fading are eliminated by automatic comparison of two or more transmissions of each message, means are provided for testing the distortion of impulses and for obliterating the distorted signals. The drawing shows the invention applied to the double-current cable-code two-channel perforating receiver shown in Fig. 4 of Specification 386,784, in which dots, dashes and spaces are respectively denoted in the incoming line by (+ +), (- - ), and (+ -) and the circuits for registering dots and dashes respectively are opened in alternate halves of the signal period under the control of cam-operated contacts. The invention may, however, be applied to other systems. Automatic comparison of twice-sent signals. The armature 1 of the receiving relay RR feeds marking signals through cam contact 6 and spacing signals through cam contact 5, the cams being out of phase as described in Specification 386,784. The dot impulses are stored through a brush in condensers h, and the dash impulses through a brush c2 in condensers k. Each impulse is sent twice in a diplex transmission ; a dot impulse belonging to the first transmission is discharged after a comparatively long storage interval by a brush g1, and the corresponding impulse belonging to the second transmission is discharged after a brief interval by brush d1. The two discharges take place simultaneously over cam-operated contacts 16, 10, which ensure that the condensers shall not be prematurely discharged. The dot discharges pass simultaneously through the respective relays 21, 23, with locking windings 29, 31, which pull up and (when the throw-over switch is in its upper position so that its wipers lie upon the upper contacts 107, 109) co-operate to close the circuit of the dot winding 48 of a neutrally biassed relay whose armature 50 supplies current via contact 55 to the inner halfwindings of the main perforator MP and spare perforator SP, which are both actuated to perforate dots. If, however, the dot signal is missing on one or other channel, one or other of the relays 21, 23 fails to act and perforation is not effected. In the case of a dash, a similar process is carried out by the charging brush c2, discharging brushes g2, d2, of the first and second channels, cam contacts 19, 13, relays 22, 24, relay winding 49, and the outer half-windings of the perforators MP, SP. The locking-circuits for the first and second transmissions respectively are broken in due course by the cam contacts 38, 37. Storage devices other than condensers (such as electromagnetic or pin- and-drum relays) may be employed. When the throw-over switch 47 is turned down the repeated transmission system ceases to act and the signals on the two channels are separately recorded by the perforators MP, SP. In a modification the segments m, n, may be in four rings, each of the two rings shown being divided into two rings for first and second channels respectively. If owing to a fault the dot and dash relays are simultaneously energized, or if the signals on the two transmissions differ, blanks are left in the tape ; an alarm signal may also be given. Obliterating distorted or overstrong signals. When the impulses of either channel are distorted or too strong (as in the case of lightning disturbances and atmospherics) impulses on both channels occurring at that time are obliterated ; reception is then controlled by the stored first-channel impulses corresponding to the obliterated second-channel impulses, and by the subsequent second-channel impulses corresponding to the obliterated first-channel impulses. The winding 63 is connected in a scrutinizing circuit of the kind described in Specification 286,365, [Class 40 (iii)], and takes the place of the alarm A, Fig. 1, of that Specification. Thus when signals are distorted the winding 63 is energized and alternatively or additionally it may be energized when the impulses are too strong, as in the case of interference from lightning. When the armature 64 is attracted it closes the locking winding 83 and also releases the ratchet 66, causing the contacts 75, 78 to be closed as shown. Charges are consequently applied through obliterating- brushes o1, o2, on both channels to all condensers that are due to receive signals at that time ; thus the control of the final relay armature 50 is left to the preceding first-channel impulses and subsequent second-channel impulses corresponding respectively to the secondchannel and first-channel impulses that have been obliterated. Obliteration continues until the locking winding 83 has been cut off at 105 by a change of polarity, as described below, and ratchet 66 has been stepped by pawl 67 during three signal periods so as to open the contacts 75, 78. Obliterating signals during a prolonged disturbance. In the case of a disturbance caused by fading, changing of a line, or insertion of a wrong plug, the subsidiary armature 96 of the receiving relay RR fails to move and the pawl. 90, which normally is withdrawn by winding 101 at every change of signal-polarity, becomes effective to check the ratchet 84, which is moved one step forward in each signal period by the pawl 85 until it closes the contacts 92, 94 so as to apply obliterating charges to the condensers. Application to various telegraph systems. The Specification describes the modifications which are necessary when the invention is to be applied to ordinary cable code or five-unit code, or to a system of the kind described in Specification 111,343, [Class 40 (iii)], in which signals are stored in movable pins on a drum.